Wednesday, February 17, 2016

I have had my vacuum chamber up and running for a while now and this allows me to degas molding and casting materials for bubble free pours. I have also made myself a vacuum form that has had teething issue - heat or suction and sometimes both. Rather than fill my work space with several pieces of equipment, I wanted to create a rig that would serve multiple uses.

The New Vacuum Pump

My first vacuum pump was a 1/4 HP, single stage, 3CFM pump that took just just under 3 mins to evacuate my current vacuum chamber. This new 1HP, 2 stage, 9CMF pump pulls a vacuum in under 1 min. So whilst this has lengthened the work time of the product, it is still not 100% perfect. Tiny bubbles of air form during the pour and sometimes get trapped on the mold surface. The ability to degas the product in the mold is appealing because it will completely eliminate these issues. To do this, I need a larger diameter chamber.

New Large Diameter Pipe Section

This new chamber still needs to be made up and will need custom bases and lids as well as an array of pluming to attach the new pump. The OD of this pipe is 800mm and the ID is 706mm. It is 150mm tall. This is large enough to allow me to place my #ClearSole molds flat inside and because I will be able to mix, pour and degas in the molds, it won't matter if it takes 2min to achieve a vacuum again.

I am also designing this chamber to be modular where a 2nd ring like this can be added to the top to make the new chamber taller for 'female tooled' vacuum and thermo forming of plastic.

Female Tooling Vacuum Forming Test.

This dome was pulled into a hollow tube. It is 250mm wide and was made from 3mm white Perspex. I did this part as a test simply using the current vacuum chamber where I achieved a seal first, created suction of about 15"HG and then proceeded to heat the plastic.

Normally when you vacuum form, you heat the plastic first, then place it over the tool and evacuate the air. You are taxed on time here as seconds could and if the seal is not good or the plastic cools too fast, you DO NOT get a get a good pull.

In this case, I the seal was perfect and as I heated the plastic to pliable state, the suction immediately pulled the plastic down. In a traditional vacuum forming heating system, the plastic tends to warp and bow upwards towards the heater. If it touches the heater, it has ruined the plastic. In this case, as soon as the plastic was pliable, it was sucked down away from the heating source.